Theoretical study of the dielectric constant in porous sandstone saturated with hydrocarbon and water

Hu, Kaijian; Liu, C.R.

doi:10.1109/36.843026

Cited by 20 publications

(14 citation statements)

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“…The effective permittivity of the site materials: groundwater (clean and contaminated), free‐phase LNAPL, and clean, subsurface sands, were evaluated in the laboratory using a dielectric analysis technique incorporating an Agilent Technologies (Santa Clara, CA) 8753ES Automated Vector Network Analyzer and a series of calibrated test cells. The technique is well established and has been used to measure a wide range of subsurface materials including soils (e.g., Shang et al, 1999; Starr et al, 1999; Heimovaara et al, 1996; Olhoeft and Capron, 1993), rocks (e.g., West et al, 2003; Chelidze et al, 1999; Fam and Dusseault, 1998; Taherian et al, 1990), and, more pertinently, hydrocarbon‐saturated materials (e.g., Hu and Liu, 2000). In this instance, the method developed by Cassidy (2001) was used, which follows the approach adopted by Baker‐Jarvis et al (1993, 1990) rather than the more commonly used Nicholson and Ross method (Nicholson and Ross, 1970; Nicholson, 1968).…”

Section: Analysis Methodologymentioning

confidence: 99%

GPR Attenuation and Scattering in a Mature Hydrocarbon Spill: A Modeling Study

Cassidy

2008

Vadose Zone Journal

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Subsurface contamination by light nonaqueous-phase liquids (LNAPLs) is a pressing environmental issue with many industrial sites having some degree of near-surface pollution. Noninvasive, geophysical investigation methods, such as ground penetrating radar (GPR), have become increasingly popular, but their use has tended to be restricted to plume "mapping" and recent contamination events only. Mature LNAPL contamination, where the hydrocarbons undergo signifi cant alteration and biodegradation, complicates the electrophysical properties of the subsurface, making GPR data interpretation more diffi cult. This is particularly true in shallow, coastal environments where LNAPLs form a disaggregated, smeared zone associated with the seasonally changing groundwaters. Therefore, any method that can improve data interpretation has a signifi cant practical benefi t in these complex environments. By using dielectric material property analysis, empirical mixing model evaluation, and threedimensional, fi nite-difference time-domain (FDTD) modeling, it has been possible to investigate the nature and spectral content of GPR signal attenuation and scattering within the vadose or smeared zone of a mature LNAPL-contaminated site. Using FDTD models to simulate real subsurface conditions, a comparison between the GPR response of "clean" and contaminated environments has been made where the subsurface materials contain different LNAPL-porewater saturations and contaminant geometries. The results show that uniform mixtures, disaggregated scattering mixtures, and stratifi ed pools of contaminated material all exhibit different, yet characterizable, temporal and spectral GPR responses and that the recorded data can provide new insights into the mode of contaminant distribution and saturation as long as the incident fi eld of the GPR system can be determined accurately.

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Section: Analysis Methodologymentioning

confidence: 99%

GPR Attenuation and Scattering in a Mature Hydrocarbon Spill: A Modeling Study

Cassidy

2008

Vadose Zone Journal

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“…High-frequency (0.1 MHz to 10 GHz) complex dielectric permittivity measurement techniques were used to quantify spatial and temporal variation of soil moisture content in a range of disciplines, including geotechnical engineering (Arulanandan 1991;Thevanayagam 1995;Klein and Santamarina 1997;Santamarina and Fam 1997;Wang and Dong 2008;Wagner and Scheuermann 2009), geoenvironmental engineering (Rowe et al 2001;Francisca and Rinaldi 2003;Shang et al 2004;Xu et al 2007), agriculture and hydrology (Cole and Cole 1941;Roth et al 1990;Tabbagh et al 2000;Wagner and Scheuermann 2009), clay science (Ishida et al 2000(Ishida et al , 2003, and geophysics (Kraszewski 1996;Hu and Liu 2000;Arcone et al 2008). The main advantage of these techniques is that they are rapid field-scale and noninvasive surveys (Roth et al 1990;Brovelli and Cassiani 2008).…”

Section: Introductionmentioning

confidence: 99%

Complex dielectric permittivity of organically modified bentonite suspensions (0.2–1.3 GHz)

Bate

Burns

2014

Can. Geotech. J.

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To quantify the impact of organic carbon on the complex dielectric permittivity of organoclays, nine organically modified clays were synthesized with controlled organic carbon structure and density of loading. Resonance polarization responses were observed for six of the organoclays at resonant frequencies from 0.74 to 1.37 GHz; however, organoclays synthesized with the smallest organic cations did not exhibit resonant frequency. A structural model of water molecules near the surface of organoclay and in the diffuse layer was proposed, which consists of a surface-bound water layer, an organic cationinteractive zone, and bulk water. The Cole-Cole equation was used to fit the resonance response. Increasing the density of loading (30% to 100% of the cation exchange capacity of the base clay) on the clay surface led to a reduction in the resonance time of the clay, while increasing the size of the organic cation led to a longer dielectric resonance time for the clay, which indicates that altering the structure and density of the organic carbon phase changed the degree of constraint of water molecules within the clay's interlayer. However, the impact of organic carbon content on real permittivity was not significant. Water content had no obvious effect on the resonant frequency of the organoclays at high water content (porosity ranging from 0.7 to 1.0) in this study. In addition, it was shown that a linear approximation was sufficient in relating real permittivity of organoclay suspensions to porosity, and the effective conductivity decreased linearly proportional to porosity. That is, the real permittivity and effective conductivity were dominated by that of the aqueous phase until the inception of resonance polarization.Résumé : Afin de quantifier l'impact du carbone organique sur la permittivité diélectrique complexe d'organo-argiles, neuf argiles modifiées organiquement ont été synthétisées avec une structure de carbone organique et une densité de charge contrôlée. Les réponses de résonance polarisée ont été observées pour six des organo-argiles à des fréquences de résonance de 0,74 à 1,37 GHz; cependant, les organo-argiles synthétisées avec les cations organiques les plus petits n'ont pas démontré de fréquence de résonance. Un modèle structural de molécules d'eau près de la surface de l'organo-argile et dans la couche diffuse a été proposé, qui consiste en une couche d'eau liée à la surface, une zone d'interaction du cation organique, et le volume d'eau. L'équation Cole-Cole a été utilisée pour représenter la réponse en résonance. L'augmentation de la densité de charge (de 30 % à 100 % de la capacité d'échange cationique de l'argile de base) sur la surface de l'argile a entraîné une réduction du temps de résonance de l'argile, tandis que l'augmentation de la taille du cation organique a entraîné un temps de résonance diélectrique plus long pour l'argile, ce qui signifie que l'altération de la structure et de la densité de la phase de carbone organique change le degré de contrainte des molécules d'eau à l'intérieu...

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“…More physically based formulas for high inclusion concentrations (Hu and Liu, 2000) fail to corne close even to the right value of a'.…”

Section: Resultsmentioning

confidence: 89%

<title>Field study of GPR attenuation rates in natural and contaminated silt</title>

Arcone

Delaney

2002

SPIE Proceedings

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GPR is considered ineffectual in penetrating silty soils. Capillary tension appears to move the interstitial water dielectric relaxation frequency near the GPR range. If hydrocarbons relieve the tension, then GPR attenuation rates should decrease. We profiled these rates across a partly contaminated quartz silt diamicton at an inactive fuel terminal in Haines, Alaska. We calculated the rates from the signal amplitude decay within a series of 400-MHz moveout surveys recorded along a single transect. We sampled the hydrocarbon content along the transect and on the wall of a trench we excavated beside it, along with water content, density and resistivity. The silt was saturated and generally at 50-80 ohm-m. The ground impedance loading brought the antenna pulse center frequency down to near 200 MHz. The rates ranged from 5 to 8 dB/m in the contaminated zone and about 10 to 15 dB/m in the uncontaminated zone. The resistivities account for the contamination rates, but a dielectric relaxation centered near 1-2 GHz, using a simple mixing model, is required to account for those in the uncontaminated zone. Hydrocarbon soil analysis suggests that the threshold level for the attenuation effect is not higher than about 1000 ppm. We suggest GPR offset surveys for assessing contamination zones.

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Theoretical study of the dielectric constant in porous sandstone saturated with hydrocarbon and water

Cited by 20 publications

References 11 publications

GPR Attenuation and Scattering in a Mature Hydrocarbon Spill: A Modeling Study

GPR Attenuation and Scattering in a Mature Hydrocarbon Spill: A Modeling Study

Complex dielectric permittivity of organically modified bentonite suspensions (0.2–1.3 GHz)

<title>Field study of GPR attenuation rates in natural and contaminated silt</title>

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